<!DOCTYPE html>
<html>
    <head>
        <meta charset="utf-8">
        <title>Example</title>
        <script>
        var toggleHidden = function() {
            var elem = document.getElementById("toggle");
            if (elem.hasAttribute("hidden")) {
                elem.removeAttribute("hidden");
            } else {
                elem.setAttribute("hidden", "hidden");
            }
        }
        </script>
    </head>
    <body>
        <button onclick="toggleHidden()">Toggle</button>
        <table>
            <tr>
                <th>
                    Name
                </th>
                <th>
                    City
                </th>
            </tr>
            <tr>
                <td>
                    Adam Freeman
                </td>
                <td>
                    London
                </td>
            </tr>
            <tr id="toggle">
                <td>
                    Joe Smith
                </td>
                <td>
                    New York
                </td>
            </tr>
            <tr>
                <td>
                    Anne Jones
                </td>
                <td>
                    Paris
                </td>
            </tr>
        </table>
    </body>
</html>
